FIG. 1 depicts a portion of a conventional read transducer 50 from the air-bearing surface (ABS) and from above. The conventional transducer 50 is a read transducer that includes a read sensor 52 and hard bias structures 64. The read sensor includes an AFM layer 54, a pinned layer that is a synthetic antiferromagnetic (SAF) layer 56, a nonmagnetic spacer layer 58, a free layer 60, and a capping layer 62. The SAF 56 includes a ferromagnetic layer (pinned layer) adjoining the AFM 54, a ferromagnetic (reference) layer and a nonmagnetic spacer layer between the pinned and reference layers. For simplicity, the pinned and reference layers are not separately depicted in FIG. 1. However, the magnetizations 55 and 57 of the pinned and reference layers, respectively, are separately shown. The magnetizations 55 and 57 are pinned perpendicular to the ABS (into or out of the plane of the page in the ABS view). The free layer 60 has a magnetization 61 biased by the magnetizations 65 of the hard bias structures 64. For clarity, the orientation 53 of the AFM layer 54 is also shown.
In operation, the read sensor 52 is exposed to an external magnetic field, for example from recording media (not shown). The external magnetic field may cause the free layer magnetization 61 to change direction. The free layer magnetization 61 would thus no longer be parallel to the hard bias magnetizations 65. As a result, the angle between the reference layer magnetization 57 (P2) and the free layer magnetization 61 changes. For low TMR, to a first approximation, the conductance of the read sensor 52 varies with the cosine of the angle between the magnetizations 57 and 61. More specifically, if θ is the angle between the reference layer magnetization 57 and the free layer magnetization 61, the conductance varies with 1+½*TMR*cos θ, where TMR is the maximum tunneling magnetoresistance. Thus, to a first approximation, the resistance of the sensor 52 varies as 1/[1+TMR*cos θ/(2+TMR)].
Although the conventional read transducer 50 may function, there are drawbacks. It has been determined that for higher TMR, the response of a magnetic element such as the sensor 52 changes. In particular, first approximation for the transfer curve of such a magnetic element as varying with case is inaccurate. Accordingly, what is needed is an improved magnetic element that may be used as the read sensor 52.